MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 157 PM EST TUE FEB 24 2015 VALID FEB 24/1200 UTC THRU FEB 28/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND THE ECMWF AND UKMET ...SHORTWAVE TROUGH CROSSING THE GREAT LAKES/NORTHEAST... ...SURFACE LOW IMPACTING EASTERN NEW ENGLAND BY EARLY WED... PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW A NORTHERN STREAM TROUGH CROSSING THE GREAT LAKES AND NORTHEAST TODAY AND WED WHICH WILL DRIVE A REINFORCING ARCTIC COLD FRONT ACROSS THE REGION. THIS ENERGY COUPLED WITH A LEAD SHORTWAVE IMPULSE WILL DEVELOP AN AREA OF LOW PRESSURE JUST OFF EASTERN NEW ENGLAND BY EARLY WED. THE 12Z UKMET IS A TAD LEFT OF THE MULTI-MODEL CONSENSUS. THE 12Z NAM IS A TAD RIGHT OF THE SAME CONSENSUS...BUT IS ALSO A LITTLE STRONGER WITH ITS MID LEVEL REFLECTION THAN THE OTHER MODELS. THE 12Z GFS/12Z GEM AND 12Z ECMWF CLUSTER VERY WELL TOGETHER IN BETWEEN THE TWO CAMPS...AND GIVEN ROBUST ENSEMBLE SUPPORT FROM THE GEFS MEAN AND ECENS MEAN...A BLEND OF THE GFS AND ECMWF WILL BE PREFERRED. ...UPPER LOW EJECTING OUT OF THE SOUTHWEST... ...SURFACE LOW DEVELOPING OVER THE GULF OF MEXICO... PREFERENCE: 12Z GFS CONFIDENCE: AVERAGE A CLOSED LOW IN THE SOUTHWEST U.S. WILL BECOME AN OPEN BUT SHARP TROUGH AS IT APPROACHES TEXAS BY WEDNESDAY. THIS WILL INDUCE A WAVE ALONG A FRONT IN THE NORTHERN GULF OF MEXICO ON WED WHICH WILL CROSS NORTHERN FLORIDA AND JUST OFFSHORE THE SOUTHEAST COAST THROUGH THURS. THE 09Z SREF GUIDANCE AND 12Z NAM COLLECTIVELY ARE THE MOST AMPLIFIED WITH THIS SYSTEM AS IT EJECTS EAST ACROSS THE GULF COAST STATES AND THROUGH THE SOUTHEAST. CONSEQUENTLY...THEY ARE FARTHER NORTH WITH THEIR RESPECTIVE LOW TRACKS. DISSECTING THE SREF GUIDANCE ITSELF...THERE ARE A NUMBER OF ARW AND NMMB MEMBERS WHICH ARE CONSIDERABLY MORE AMPLIFIED AND FARTHER NORTH WITH THEIR LOW TRACKS VERSUS THE NMM MEMBERS...AND SO THE FULL ENSEMBLE MEAN AS A RESULT IS MORE AGGRESSIVE IN BEING FARTHER NORTH AND WETTER. CONVERSELY...THE 12Z GFS/12Z ECMWF/12Z UKMET AND 12Z GEM ARE ALL MORE SUPPRESSED AND WEAKER. THE GEM IS THE MOST SUPPRESSED OF THIS CLUSTER...WITH THE GFS AND UKMET MODESTLY STRONGER AND SHARPER...BUT NOT TO THE EXTENT OF THE SREF/NAM GUIDANCE. THE 12Z ECMWF IS CLOSE TO THE 12Z GFS...BUT IS JUST A TAD SLOWER. BASED ON THE SPREAD...ENSEMBLE SUPPORT AND TRENDS...WILL CONTINUE TO FAVOR THE 12Z GFS FOR MASS FIELDS. ...STRENGTHENING TROUGHING OVER THE GREAT LAKES/NORTHEAST THROUGH FRI... PREFERENCE: NON-UKMET CONSENSUS CONFIDENCE: ABOVE AVERAGE THE MODELS FEATURE SIMILAR HANDLING OF ANOTHER IS A SERIES OF DEEP NORTHERN STREAM TROUGHS TO CROSS THE NORTHERN TIER OF THE COUNTRY. THIS NEXT TROUGH WILL CROSS THE UPPER MIDWEST AND GREAT LAKES REGION WED AND THURS...AND THEN REACH THE NORTHEAST ON FRI. THIS WILL LEAD THE WAY FOR ANOTHER ARCTIC SURFACE HIGH TO NOSE SOUTH THROUGH THE PLAINS AND MIDWEST. THE 12Z UKMET DOES GRADUALLY BECOME A LITTLE STRONGER THAN THE MULTI-MODEL CONSENSUS BY FRI AS THE ENERGY REACHES THE NORTHEAST. WILL FAVOR A NON-UKMET CONSENSUS AS A RESULT. ...TROUGH AMPLIFYING OVER THE NORTHWEST THURS AND FRI... PREFERENCE: BLEND OF THE 12Z ECMWF AND 00Z ECENS MEAN CONFIDENCE: BELOW AVERAGE AS A CLOSED LOW EXITS THE SOUTHWEST U.S...HEIGHTS GENERALLY RISE ALONG THE WEST COAST AND INTERMOUNTAIN REGION...BUT WITH SOME BUCKLING OF THE NORTHWESTERLY FLOW AS PACIFIC SHORTWAVES DIVE FROM THE NORTHWEST U.S. TOWARD THE SOUTHERN ROCKIES. A MORE AMPLIFIED SHORTWAVE IS FORECAST TO DIG INTO THE NORTHWEST BY FRI. THE 12Z UKMET BECOMES THE MOST AMPLIFIED SOLUTION WITH A LARGE CLOSED LOW DEVELOPING BY FRI OVER OR/CA. THE 12Z ECMWF AND 12Z GEM ARE NOT QUITE AS AMPLIFIED AND ARE A BIT SLOWER TO DIG ENERGY SOUTH DOWN THE WEST COAST...BUT THEY ARE GENERALLY STRONGER THAN THE 12Z NAM AND ESPECIALLY THE 12Z GFS. THE 12Z GEFS MEAN SUPPORTS THE DETERMINISTIC GFS...WITH THE 00Z ECENS MEAN FAVORING THE DETERMINISTIC ECMWF. OVERALL...THE TRENDS IS FOR A SOMEWHAT MORE AMPLIFIED TROUGH DIGGING DOWN THROUGH THE WEST...AND SO AT THIS POINT WILL FAVOR A BLEND OF THE 12Z ECMWF AND 00Z ECENS MEAN. CONFIDENCE IS LIMITED GIVEN THE AMOUNT OF HEIGHT FALL SPREAD AT THE END OF THE PERIOD. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON